The present invention relates to a novel carbon-based metal composite material, a method for its production and various applications using said carbon-based metal composite material. In more detail, it relates to a carbon-based metal composite material comprising a carbonaceous matrix and metal components dispersed in said carbonaceous matrix, a method of impregnating a carbon material with metal components, and uses of a carbon-based metal composite material, such as high thermal conductivity-low, thermal expansivity substrates for packaging semi-conductors, astronautical components or general industrial structural materials having excellent specific strength and specific rigidity, heat resistant materials such as for gas turbines, and electrical contact materials having excellent sliding characteristics.
Conventional metal composite materials containing carbon materials are produced by dispersing and orientating carbon particles or carbon fibers, as reinforcing materials, in a metal component matrix. Furthermore, there have been adopted production methods according to the so-called powder metallurgy method using graphite powder and metal powder as starting materials.
These types of metal-carbon composite materials each use carbon materials to try to improve the characteristics of the metal component, as the parent material for the composite material, and should be called metal-based carbon composite materials having a metal component as the parent material. Such materials having a much larger volume of carbon than metal component have not been realised, and these materials are therefore themselves limited in their performance.
On the other hand, carbon materials have been widely used as result of their excellent heat resistance and workability. However, they have many points that need to be improved such as being brittle, having low strength, being easily damaged, having low oxidation resistance, being difficult to plate, and having low heat conductivity. One reason for this is that, with the exception of special carbon materials, carbon materials generally have pores, as a result of which the electrical, heat and chemical properties naturally possessed by carbon are not fully exhibited.
It has been attempted to improve the characteristics of carbon materials by filling the pores of the carbon material with metal material thereby forming a carbon-metal composite. For example, a material having some of the pores substituted with molten copper, copper alloy or silver has been proposed in order to improve the electrical characteristics of carbon materials. However, it was impossible to obtain a material having a large portion of the pores substituted with metal, and its performance was not sufficient.
In general, carbon materials and molten metals have poor wettability, and it was almost impossible in previous studies to impregnate the pores of carbon materials with molten metal components. Although the wettability was improved at high temperatures, casting impregnation at high temperatures resulted in a reaction between the carbon component and the metal component. This resulted in a deterioration in the carbon material, with the problem that it was impossible to obtain the characteristics of a metal-based carbon composite material.
In other words, the production of a composite by the impregnation of a carbon material with metal components by a production method according to the conventionally proposed conditions and operations results in a reaction at the interface between the carbon component and the metal component and the generation of the metal carbide. This had, for example, the ill effect of these two components peeling away from each other, and a carbon-based metal composite material having excellent strength and other properties had not been developed.
Along with the technical development of this type of metal-carbon composite materials, there has been an increase in the amount of heat generated by electronic devices as a consequence of their improved performance and capacity, and there has been a focus on carbon-based metal composite materials having a high proportion of carbon component and having excellent strength as a high thermal conductivity-low thermal expansivity material effective for heat removal. The development of these materials is now eagerly anticipated.
A first objective of the present invention is, in light of the above-mentioned problems with the techniques developed to date, to provide a carbon-based metal composite material which maintains a high degree of heat resistance and high thermal conductivity as well as having a controlled thermal expansivity and excellent strength.
A second objective of the present invention is to provide a method of producing a carbon-based metal composite material comprising impregnating a molten metal into the pores of a carbon formed body whilst inhibiting reactions between carbon and the metal:
Furthermore, a third objective of the present invention is to provide a material for an electronic component having a high thermal conductivity and a controlled thermal expansivity useful for the removal of heat from an electronic component.
A fourth objective of the present invention is to provide a carbon-based metal composite material provided with an insulator film.
The inventors of the present invention have found, as result of extensive research into achieving the above-described objectives, that a high thermal conductivity-low thermal expansivity composite material can be obtained by impregnating the pores of a carbon material with a metal component under molten and pressurized conditions, and that the above-described objectives can be achieved using the same. It was on the basis of these findings that the present invention was completed.
In other words, the present invention firstly relates to a carbon-based metal composite material comprising a carbonaceous matrix and a metal component dispersed in said carbonaceous matrix characterised in that
(1) at least 90 volume percent of the pores of said carbonaceous matrix are substituted with said metal component, and
(2) the content of said metal component is 35% or less based on the total volume of said carbon-based metal composite material.
Furthermore, the present invention secondly relates to a method of producing a carbon-based metal composite material comprising impregnating a carbon formed body with a molten metal by contacting said carbon formed body with said molten metal under pressure, characterised in that
(1) said carbon formed body is pre-heated to a temperature at or above the melting point of said molten metal under an inert gas atmosphere; and
(2) said pre-heated carbon formed body is impregnated with said molten metal under a pressure of at least 200kg per cm2 of the cross-sectional area of the plunger.
Furthermore, the present invention thirdly relates to a substrate-shaped formed body for an electronic component characterised in that it is formed from a carbonaceous metal composite material comprising a carbonaceous matrix and a metal component dispersed in said carbonaceous matrix, wherein at least 90 volume percent of the pores of said carbonaceous matrix are substituted with said metal component, and the content of said metal component is 35% or less based on the total volume of said carbonaceous metal composite material.
Furthermore, the present invention fourthly relates to a carbon-based metal composite material provided with an insulator film obtained by covering the surface of a carbonaceous metal composite material with an insulator material, the carbonaceous metal composite material having a carbonaceous matrix and a metal component dispersed in said carbonaceous matrix, wherein at least 90 volume percent of the pores of said carbonaceous matrix are substituted with said metal component, and the content of said metal component is 35% or less based on the total volume of said carbonaceous metal composite material.